How a road train could work The driver's sat-nav indicates that there is a road train ahead that is following some of his/her planned journey. The driver approaches the road train, which is controlled by a professional driver at the front, and indicates that he/she wishes to join. The road train takes control of the extra car, pulling it close to cut air drag and save about 20% in fuel consumption. The drivers can relax until they wish to leave the road train, at which point they signal their intention to the driver at the front. A bigger gap will be made to allow the car to leave and control of the vehicle will be returned to that driver. Road trains that link vehicles together using wireless sensors could soon be on European roads. An EU-financed research project is looking at inexpensive ways of getting vehicles to travel in a 'platoon' on Europe's motorways. Each road train could include up to eight separate vehicles - cars, buses and trucks will be mixed in each one. The EU hopes to cut fuel consumption, journey times and congestion by linking vehicles together. Early work on the idea suggests that fuel consumption could be cut by 20% among those cars and trucks travelling behind the lead vehicle. Spanish trials The lead vehicle would be handled by a professional driver who would monitor the status of the road train. Those in following vehicles could take their hands off the wheel, read a book or watch TV, while they travel along the motorway. Their vehicle would be controlled by the lead vehicle. Funded under the European Commission's Framework 7 research plan, Sartre (Safe Road Trains for the Environment) is aimed at commuters in cars who travel long distances to work every day but will also look at ways to involve commercial vehicles. Tom Robinson, project co-ordinator at engineering firm Ricardo, said the idea was to use off-the-shelf components to make it possible for cars, buses and trucks to join the road train. "The goal is to try and introduce a step change in transport methods," he said. "We're looking at what it would take to get platooning on public highways without making big changes to the public highways themselves," said Mr Robinson. A system that involved wiring up motorways with sensors to help control the road trains would be prohibitively expensive, he said. "Each of the vehicles will have their own control and software monitoring system," said Mr Robinson. "There may well be a platoon sensor envelope that collates information and presents it to the lead vehicle so it can understand what is happening around all the vehicles." The idea is to make platoons active so vehicles can join and leave as they need. Mr Robinson speculated that those joining a platoon or road train may one day pay for the privilege of someone else effectively driving them closer to their destination. Sartre will run for three years. The project partners are currently doing preliminary research to find out all the elements needed for a working system and the situations in which it might be used. There were also behavioural elements to consider, said Mr Robinson, such as whether all the vehicles will need to have their hazard lights on while in a platoon. Also, he said, there had to be a way to ensure the vehicles in a platoon are organised to make drivers feel safe. "Car drivers do not want to be between trucks," he said. Towards the end of the research project trials will be held on test tracks in the UK, Spain and Sweden. There are also plans for public road trials in Spain. The first platoon will involve two trucks and three cars.